Context Studios
Provider Comparison

Claude Opus 5 vs. Claude Fable 5.1 (2026): Half the Price Against the New Peak

Claude Opus 5 vs Claude Fable 5 in 2026: list price, cost per completed task, knowledge cutoff, caching and where Fable still holds the peak.

5
The new default
vs
3
The frontier ceiling
Quick Verdict

Until September, the case for Opus 5 was simple: half the price, within half a percent of Fable's peak. Claude Fable 5.1 has dissolved the second half of that sentence — on Artificial Analysis it is now the leading model (66 Intelligence Index points, five ahead of GPT-6 Astra and Sol), and on CursorBench 3.2 it is the most capable model Cursor has ever run. The price argument, however, fully holds: Opus 5 lists at $5/$25 and remains the right default for standard workloads. It just costs something new: Fable 5.1's $0.25/MTok cache reads (down from $1) make the Fable line clearly more affordable exactly where it used to hurt most — cache-heavy agentic long runs, research, multi-turn coding. Practical rule: default to Opus 5, escalate to Fable 5.1 for long agent loops and frontier judgment — and re-measure instead of trusting last spring's price-per-point tables.

Detailed Comparison

A side-by-side analysis of key factors to help you make the right choice.

Factor
The new defaultRecommended
The frontier ceilingWinner
List API price
$5 per million input tokens, $25 per million output tokens.
$10 per million input tokens, $50 per million output tokens — exactly double.
Cost per completed task
On CursorBench 3.2 at max effort it lands within 0.5% of Fable 5's peak score at half the cost per task; on OSWorld 2.0 it beats Fable 5's best result at just over a third of the cost.
Holds the peak score on those same benchmarks, but pays roughly two to three times as much per completed task to get there.
Ceiling on the hardest tasks
Anthropic's own wording is "comes close to" the frontier — near-frontier, by the vendor's own description.
Still the top of the Claude range, and the Mythos class remains ahead of Opus 5 on cybersecurity evaluations.
Knowledge freshness
Reliable knowledge cutoff May 2026.
Reliable knowledge cutoff January 2026 — four months older.
Caching economics
Cache hits and refreshes at $0.50 per million tokens, and the minimum cacheable prompt drops to 512 tokens.
Cache hits and refreshes at $1 per million tokens, with the usual 1,024-token minimum.
Latency profile
Rated "moderate" on Anthropic's comparative-latency scale.
Rated "slower" — the price of the extra ceiling.
Context window and output limit
1M-token context window (both the default and the maximum, no smaller variant) and 128k maximum output.
1M-token context window and 128k maximum output — identical.
Strength of the evidence
Two days old at the time of writing: the headline numbers are Anthropic's own charts, and BenchLM lists its #1 placement with an "Estimated" evidence label.
Generally available since June 2026, with a public track record; BenchLM lists its #3 placement as "Supported".
The Fable 5.1 refresh (September 2026)
Opus 5 stays at $5/$25 — still half of Fable 5.1's list price and the cheaper default for standard workloads.
Fable 5.1 reopens the capability gap: current #1 on the AA Intelligence Index (66), the most capable model Cursor has ever run on CursorBench 3.2 (73.4%), and cache reads drop from $1 to $0.25/MTok — a steep effective-price cut exactly where Fable used to hurt most, in cache-heavy agentic long runs.
Total Score5/ 93/ 91 ties
List API price
The new default
$5 per million input tokens, $25 per million output tokens.
The frontier ceiling
$10 per million input tokens, $50 per million output tokens — exactly double.
Cost per completed task
The new default
On CursorBench 3.2 at max effort it lands within 0.5% of Fable 5's peak score at half the cost per task; on OSWorld 2.0 it beats Fable 5's best result at just over a third of the cost.
The frontier ceiling
Holds the peak score on those same benchmarks, but pays roughly two to three times as much per completed task to get there.
Ceiling on the hardest tasks
The new default
Anthropic's own wording is "comes close to" the frontier — near-frontier, by the vendor's own description.
The frontier ceiling
Still the top of the Claude range, and the Mythos class remains ahead of Opus 5 on cybersecurity evaluations.
Knowledge freshness
The new default
Reliable knowledge cutoff May 2026.
The frontier ceiling
Reliable knowledge cutoff January 2026 — four months older.
Caching economics
The new default
Cache hits and refreshes at $0.50 per million tokens, and the minimum cacheable prompt drops to 512 tokens.
The frontier ceiling
Cache hits and refreshes at $1 per million tokens, with the usual 1,024-token minimum.
Latency profile
The new default
Rated "moderate" on Anthropic's comparative-latency scale.
The frontier ceiling
Rated "slower" — the price of the extra ceiling.
Context window and output limit
The new default
1M-token context window (both the default and the maximum, no smaller variant) and 128k maximum output.
The frontier ceiling
1M-token context window and 128k maximum output — identical.
Strength of the evidence
The new default
Two days old at the time of writing: the headline numbers are Anthropic's own charts, and BenchLM lists its #1 placement with an "Estimated" evidence label.
The frontier ceiling
Generally available since June 2026, with a public track record; BenchLM lists its #3 placement as "Supported".
The Fable 5.1 refresh (September 2026)
The new default
Opus 5 stays at $5/$25 — still half of Fable 5.1's list price and the cheaper default for standard workloads.
The frontier ceiling
Fable 5.1 reopens the capability gap: current #1 on the AA Intelligence Index (66), the most capable model Cursor has ever run on CursorBench 3.2 (73.4%), and cache reads drop from $1 to $0.25/MTok — a steep effective-price cut exactly where Fable used to hurt most, in cache-heavy agentic long runs.

Key Statistics

Real data from verified industry sources to support your decision.

Claude Opus 5 lists at $5 / $25 per million input and output tokens, Claude Fable 5 at $10 / $50 — exactly double

Claude Platform Docs — Pricing

Claude Platform Docs — Pricing (2026)
On CursorBench 3.2 at max effort, Opus 5 scores within 0.5% of Fable 5's peak at half the cost per task

Anthropic — Introducing Claude Opus 5

Anthropic — Introducing Claude Opus 5 (2026)
On OSWorld 2.0, Opus 5 surpasses Fable 5's best result at just over a third of the cost

Anthropic — Introducing Claude Opus 5

Anthropic — Introducing Claude Opus 5 (2026)
On ARC-AGI 3, Opus 5 scores three times as high as the next-best model

Anthropic — Introducing Claude Opus 5

Anthropic — Introducing Claude Opus 5 (2026)
Reliable knowledge cutoff: May 2026 for Opus 5 against January 2026 for Fable 5, with both models on a 1M-token context window

Claude Platform Docs — Models overview

Claude Platform Docs — Models overview (2026)
Public leaderboard placement: Opus 5 at #1 carries an "Estimated" evidence label, Fable 5 at #3 a "Supported" one

BenchLM

BenchLM (2026)
Anthropic price list (as of 2026-09-04): cache reads cost 0.025× the base input price on Claude Fable 5.1 and Mythos 5.1 — $0.25/MTok against $1/MTok on Claude Fable 5 — a 4× cut of the dominant cost inside cache-heavy agent loops.

Anthropic docs — pricing

Anthropic docs — pricing (2026)
Artificial Analysis (2026-09-03): Claude Fable 5.1 (max with fallback) scores 66 on the Intelligence Index — current #1, five points ahead of GPT-6 Astra and GPT-5.6 Sol (61 each).

Simon Willison / Artificial Analysis

Simon Willison / Artificial Analysis (2026)
Cursor (2026-09-02/03): Fable 5.1 reaches 73.4% at max effort on CursorBench 3.2 — the most capable model Cursor has run on that benchmark to date.

Cursor AI (@cursor_ai on X)

Cursor AI (@cursor_ai on X) (2026)

All statistics come from verified third-party sources. Source, year, and direct link are shown on each metric.

When to Choose Each Option

Clear guidance based on your specific situation and needs.

Choose The new default when...

  • You run high-volume agentic or coding work where the cost per completed task decides the budget, not the top of a leaderboard.
  • Your agents lean on prompt caching: the $0.50 cache-hit rate and the 512-token cache minimum compound across long sessions.
  • Your workload touches anything between January and May 2026 and you would otherwise pay for retrieval to close that gap.
  • You are already on Opus 4.8 — Opus 5 costs the same, so the upgrade is an evaluation question, not a budget request.

Choose The frontier ceiling when...

  • You need the highest available score on the hardest tasks and the last half percent is worth paying double for.
  • Your evaluation policy requires a public track record: Fable 5 has been generally available since June 2026, Opus 5 for days.
  • Your work is security-heavy — the Mythos class remains ahead of Opus 5 on cybersecurity evaluations.
  • Your pipeline is tuned and validated against Fable 5's behaviour and a full re-evaluation would cost more than the price difference saves.

Our Recommendation

Until September, the case for Opus 5 was simple: half the price, within half a percent of Fable's peak. Claude Fable 5.1 has dissolved the second half of that sentence — on Artificial Analysis it is now the leading model (66 Intelligence Index points, five ahead of GPT-6 Astra and Sol), and on CursorBench 3.2 it is the most capable model Cursor has ever run. The price argument, however, fully holds: Opus 5 lists at $5/$25 and remains the right default for standard workloads. It just costs something new: Fable 5.1's $0.25/MTok cache reads (down from $1) make the Fable line clearly more affordable exactly where it used to hurt most — cache-heavy agentic long runs, research, multi-turn coding. Practical rule: default to Opus 5, escalate to Fable 5.1 for long agent loops and frontier judgment — and re-measure instead of trusting last spring's price-per-point tables.

Frequently Asked Questions

Common questions about this comparison answered.

On most published evaluations Opus 5 leads, and Anthropic calls it state of the art on coding and knowledge-work benchmarks such as Frontier-Bench and GDPval-AA. But the vendor's own phrasing is that Opus 5 "comes close to" Fable 5's frontier intelligence, and on CursorBench 3.2 the peak score still belongs to Fable 5 — Opus 5 gets within 0.5% of it for half the cost. If you optimise for intelligence per euro, Opus 5 wins clearly. If you optimise for the absolute ceiling, Fable 5 has not been displaced.
Exactly half on list price: $5 / $25 per million input and output tokens against $10 / $50, and cache hits at $0.50 against $1. On Anthropic's own task-level measurements the gap is similar or larger — half the cost per task on CursorBench 3.2, just over a third on OSWorld 2.0. One exception matters: Fast mode for Opus 5, currently a research preview on the Claude API only, is priced at $10 / $50, which is exactly Fable 5's rate.
No. Both run a 1M-token context window and a 128k-token maximum output. On Opus 5 the 1M window is both the default and the maximum, with no smaller variant to choose. The real differences are price, comparative latency (moderate against slower), the knowledge cutoff, and how each model handles thinking and effort.
Three things. Thinking is on by default on Opus 5, and max_tokens is a hard limit on thinking plus response text, so revisit any max_tokens value tuned for a non-thinking setup. The effort ladder — low, medium, high, xhigh, max — is your quality-versus-cost dial, and Anthropic recommends starting at the default of high and adjusting from your own evaluations. And run those evaluations: the published margins are two days old and largely first-party.
In early September 2026 Anthropic refreshed the Fable line: Fable 5.1 is currently #1 on the Artificial Analysis Intelligence Index (66, ahead of GPT-6 Astra and GPT-5.6 Sol at 61), and Cursor calls it the most capable model it has run on CursorBench 3.2 (73.4% at max effort). The cost headline: cache reads fall from $1 to $0.25 per million tokens. Opus 5 remains the cheaper default at $5/$25 list — but the 'half a percent off the peak' claim referred to the old Fable 5.

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